1. Field of the Invention
The present invention relates to a device and a method for restoring positional information of a robot, in which positional information with respect to a reference position of an articulation axis of the robot is restored.
2. Description of the Related Art
A robot with an articulation axis rotated by a motor driving typically includes a sensor outputting a sensor signal according to a motor driving amount. After the articulation axis of the robot is positioned at a reference position, a correlation between the sensor signal and an axial angle of the articulation axis is determined. Typically, this positioning is often carried out based on the fact that, when the robot is put in a predetermined orientation (position), the articulation axis is also put in a predetermined state. In order to put the robot in a predetermined orientation (position), various techniques, such as using a jig according to a structure of the robot mechanism are known. As an example, Japanese Unexamined Patent Publication No. 63-278787 (JP63-278787A) describes a method, in which a pair of structures constituting an articulation axis are provided with respective pin holes, and a pin is inserted into the respective pin holes to specify a reference position. As another example, Japanese Unexamined Patent Publication No. 2005-177962 (JP2005-177962A) describes a method, in which one of structures constituting an articulation axis is provided with a V-shaped groove and the other of structures is provided with a proximity sensor corresponding to the V-shaped groove to identify a reference position depending on a signal from the proximity sensor.
In the robot of this type, if a motor, a reduction gear coupled to the motor and the like is removed or replaced for maintenance, etc., the positional information depending on the sensor signal based on the reference position is invalidated. Therefore, in order to validate the positional information depending on the sensor signal, a positioning work and the like is necessary. However, in the method described in JP63-278787A, because the relative position of the pin holes may deviate due to an insufficient processing accuracy of the pin hole portions, an assembly error of the articulation part and the like, the positioning work is not easy and the positioning accuracy is likely to be reduced. On the other hand, in the method described in JP2005-177962A, because the proximity sensor has to be installed with respect to the direction of movement of the articulation axis with high accuracy, time and effort are necessary for the positioning thereof.